1. Field of the Invention
This invention relates to an infrared zoom lens suitable for infrared rays over a wavelength range of, in particular, either 3 to 5 .mu.m or 8 to 12 .mu.m.
2. Description of Related Art
There have been proposed various infrared zoom lenses for use with a mirror scanning type of infrared optical system. Some of such infrared zoom lenses are known and are more fully disclosed in, for example, U.S. Pat. No. 4,411,488, No. 4,632,498, No. 4,659,171, No. 4,676,581 and No. 5,022,724. However, there has been no high speed and high performance infrared zoom lenses suitable for use with a two-dimensional area sensor or detector, such as the Schottky-barrier type of charge coupled device (CCD) and the hybrid type of charge coupled device (CCD) which have the advantage that no mechanical parts such as a scanning mirror are needed and high sensitivity is expected.